BLBS102-c20 BLBS102-Simpson March 21, 2012 13:35 Trim: 276mm X 219mm Printer Name: Yet to Come
368 Part 3: Meat, Poultry and SeafoodsTable 20.2.Amino Acid Composition of Collagen from Fish and Mammalian (Residues per 1000 residues)Cod(a) Bigeye Snapper(b) Skate(c) Grass Carp(d) Pagus Major(e) Porcine(e) Calf(f)Amino Acids Skin Skin Bone Muscle Skin Scale Dermis SkinAlanine 107 136 129 115 135 133 115 119
Arginine 54 60 46 51 57 49 48 50
Aspartic acid/
asparagine53 51 47 36 42 43 44 45Cysteine 0 0 0 0 4 0 0 0
Glutamic acid/
glutamine80 78 74 78 61 71 72 75Glycine 342 286 361 356 334 346 341 330
Histidine 8 10 6 8 5 5 7 5
Isoleucine 12 5 5 17 10 7 10 11
Leucine 22 24 25 22 22 18 22 23
Lysine 29 31 25 25 23 26 27 26
Hydroxylysine 7 10 20 6 8 7 7 7
Methionine 15 12 8 9 10 15 6 6
Phenylalanine 12 15 12 12 17 13 12 3
Hydroxyproline 51 77 68 74 65 73 97 94
Proline 103 116 95 83 121 107 123 121
Serine 59 36 34 46 39 41 33 33
Threonine 23 29 25 36 24 24 16 18
Tyrosine 4 4 2 2 2 3 1 3
Valine 19 22 17 25 31 19 22 21
Imino acida 154 193 163 157 186 180 220 215Source: (a) Duan et al. (2009) (b) Kittiphattanabawon et al. (2005), (c) Mizuta et al. (2002), (d) Zhang et al. (2007), (e) Ikoma et al. (2003), and
(f) Giraud-Guille et al. (2000).
aImino acids include proline and hydroxyproline.which is almost devoid of tryptophan. Fish muscle, skin, bone,
and scale collagen differ from bovine and porcine hide colla-
gens in having significantly higher contents of seven essential
amino acids (Sikorski et al. 1990). Collagen is the only protein
that is rich in hydroxyproline (up to 10% in mammalian colla-
gen) (Sikorski et al. 1990). On the other hands, hydroxyproline
is present in negligible amounts in other proteins, thus it is of-
ten used as a measure of collagen content in foods (Foegeding
et al. 1996). Proline and hydroxyproline, imino acids, contents
vary with species and their living habitat (Foegeding et al. 1996,
Jongjareonrak et al. 2005, Kittiphattanabawon et al. 2005). Fish
collagens contain less imino acids than do mammalian coun-
terpart (Table 20.2). Lower content of imino acids is generally
found in cold-water fish, compared with warm-water fish. Imino
acids contribute to the stability of helix structure of collagen
(Ikoma et al. 2003, Jongjareonrak et al. 2005). Pyrrolidine rings
of proline and hydroxyproline impose restrictions on the con-
formation of the polypeptide chain and help to strengthen the
triple helix (Wong 1989, Bae et al. 2008). The hydroxyl group of
the hydroxyproline plays a role in stabilizing the helix by inter-
chain hydrogen bonding via a bridging water molecule as well as
direct hydrogen bonding to a carbonyl group (Wong 1989). Inter-
chains betweenα-chains of collagen, in which hydroxyproline
is involved in bondings are illustrated in Figure 20.2. Hydrox-
ylysine of 6–20 residues/1000 residues is found in collagens,suggesting the partial cross-linking of collagen via covalent
bond (Mechanic et al. 1987). Transition temperature of colla-
gen from tropical fish is generally higher than that from cold-
or temperate-water fish (Muyonga et al. 2004, Nalinanon et al.
2010). Differential scanning calorimetric study revealed the dif-
ferences in maximal transition temperature (Tm) among collagen
from different sources (Table 20.5). Therefore, collagen from
different sources might have the different molecular properties
due to the difference in imino acid content and cross-linking.
Collagen contains carbohydrates such as glucose and galac-
tose. Other sugars are also found in some fish and inverte-
brate collagens. These are attached to hydroxylysine residues
of the peptide chain byO-glycosidic bonds. The presence of
2-O-α-d-glucosyl-O-β-d-galactosyl-hydroxylysine and ofO-β-
d-galactosyl-hydroxylysine has been confirmed (Belitz et al.
2004). Some fish and invertebrate collagens also contain small
amounts of arabinose, xylose, and ribose residues (Kimura
1972). These hydroxylysine-linked carbohydrates may have an
impact on the structure of the fibrils in the invertebrate collagen
(Sikorski et al. 1990).ISOLATION OF COLLAGEN
Isolation of collagen is generally separated into three main
steps, including sample preparation, extraction, and recovery.